The invention relates to a circuit arrangement for an electronic clock with an alarm device, comprising a stepper motor, driven by a quartz oscillator with an associated frequency divider, which stepper motor drives the display elements, and comprising a PXE (piezoelectric oxide) element which generates the alarm signal.
Such circuit arrangements are generally known. FIG. 1 shows an example of one such prior art circuit. An electronic circuit 1, which is not shown in more detail, generally an integrated circuit (IC), in conjunction with a quartz resonator 2 and a voltage source 3, generates a constant frequency, which after multiple division supplies a second-pulse to a stepper motor 4, which moves the display elements, not shown, for example the hands. A switch 5, which is mechanically coupled to the hour-hand, actuates an alarm device at a preset time, which device in the present example comprises an inductance 6, a PXE (piezoelectric oxide) element 7, and a transistor 8. When the switch 5 is closed at the preset alarm time, a frequency of 4.194 kHz, derived from the frequency divider, is applied to the base of the transistor 8, so that the PXE (piezoelectric oxide) element 7 (electromechanical piezoelectric oxide transducer) generates audible vibrations, the inductance 6 constituting the d.c. path for the transistor 8.
The control pulses for the stepper motor 4 may, for example, have a duration of 1/32 sec., as is indicated in FIG. 1 at the bottom right.